Large commercial aircraft are commonly powered by extremely large turbofan jet engines. Such jet engines are commonly connected to a wing through a suitable pylon, if wing mounted, and have a suitable nacelle system which encloses and streamlines the aircraft jet engine. Such nacelle systems are broadly considered to include a nose cowl, a fan cowl, a core cowl, and a thrust reverser. The fan cowl, the thrust reverser and the core cowl are commonly hinged so that when it is necessary to perform maintenance or to have other required access to the engine or to the nacelle system itself when the aircraft is on the ground, the hinged portion may be opened in order to afford such access.
In the U.S. Pat. No. 3,511,055, issued to R. H. Timms on May 12, 1970 for THRUST REVERSER, it will be seen that it is common to hinge such sections of the nacelle system along the upper spine of the nacelle system. A bifurcated hinged section can then be unlocked along a lower spine and opened a predetermined distance to afford easy access to the engine. In order for the hinged section to remain open, a suitable hold open rod is provided. This hold open rod is carried within the nacelle system and then used to hold the hinged section open as required.
Difficulties have been encountered in the manufacture and use of such hold open rods since they are subject to frequent failure in the field. Because of space requirements, such hold open rods are often collapsible, and in use are prone to collapse at inopportune times. Because the hinged sections of the nacelle system have now grown to be quite large, the collapse of a hold open rod and the unexpected closing of the hinged section of the nacelle system can cause severe injury to a workman who is engaged in working on an engine while a hinged section of the nacelle system is open. Prior to the present invention, no hold open rod had been presented that was simple and inexpensive to manufacture and which afforded a high degree of safety and use.
The prior art reveals a number of devices that are used to adjustably position a telescoping structure to a predetermined height. Examples of these patents are seen in U.S. Pat. Nos. 2,514,095; 2,820,626; 1,725,312; 1,890,423; 2,844,348; and 2,605,117. German patent No. 866,544 issued July 8, 1949 was concerned with a similar subject. The Schreiber U.S. Pat. No. 2,514,095 is typical of this prior art. The Schreiber patent discloses an adjustable trestle jack having a swing hook which is selectively positioned within anyone of the number of annular grooves provided at intervals within a central plunger shaft. While such a device is satisfactory for a trestle jack where an object is held at a predetermined height, it does not meet the requirements for a hold open rod for hinged sections of a nacelle system of an aircraft jet engine. Due to the large area of such hinged sections, they can be raised by a sudden gust of wind thereby allowing a lock in a hold open rod to disengage or a workman engaged in maintenance of the engine can inadvertently strike a hold open rod thereby disengaging a lock feature. Thus, because of the inadvertent contact with the hold open rod by a workman or an unexpected movement of the hinged nacelle section itself it is necessary to provide a hold open rod having a locking mechanism which is ultra safe in operation. It is believed that such an ultra safe operation is provided by the present invention.